Method of making an electric motor armature core

ABSTRACT

An armature core assembly in which the heads of the circumferentially spaced T-shaped teeth that form the peripheral oortion of the laminated coilreceiving core have their opposite end portions taperingly deformed to widen the entrances to the reentrant coil receiving spaces or slots between the T-shaped teeth at opposite ends of the core. A preformed plastic shield or cap of the same size and shape as the laminations which comprise the core, completely covers each end of the core and has protective flanges that embrance the ends of its T-shaped teeth, including the head, the taperingly reduced width of the end portions of the head providing space for those portions of the protective flanges that embrace the heads, so that the presence of these protective flanges does not objectionably reduce the width of the entrances to the wire receiving slots.

United States Patent [191 Boyd et al.

[451 Aug. 27, 1974 METHOD OF MAKING AN ELECTRIC MOTOR ARMATURE CORE [21]Appl. No.: 420,940

[52] US. Cl 29/598, 29/205 D, 29/525,

[51] Int. Cl. H02k 15/02 [58] Field of Search 29/596, 598, 609, 205D,29/525; 310/216, 264; 72/363 [56] References Cited UNITED STATES PATENTS3,762,041 10/1973 Bair 29/596 3,768,152 10/1973 Swanke et al 29/596Primary ExaminerCharles W. Lanham Assistant Examiner-Carl E. Hall [57]ABSTRACT An armature core assembly in which the heads of thecircumferentially spaced T-shaped teeth that form the peripheral oortionof the laminated coilreceiving time have their opposite end portionstaperingly deformed to widen the entrances to the reentrant coilreceiving spaces or slots between the T-shaped teeth at opposite ends ofthe core. A preformed plastic shield or cap of the same size and shapeas the laminations which comprise the core, completely covers each endof the core and has protective flanges that embrance the ends of itsT-shaped teeth, including the head, the taperingly reduced width of theend portions of the head providing space for those portions of theprotective flanges that embrace the heads, so that the presence of theseprotective flanges does not objectionably reduce the width of theentrances to the wire receiving slots.

10 Clains, 6 Drawing Figures 1' METHOD OF MAKING AN ELECTRIC MOTORARMATURE CORE They are of course identical in size and'shape with avcircle of T-shaped teeth forming the peripheral portion thereof.Accordingly, when a stack of these laminations. is assembled on theshaft, they formacylindrical body that has circumferentially spacedreentrant axially extending slots into which wire is wound into a seriesof coils.

The-wire is wound onto the laminated body or core by automaticarmature'winding machinesv in which a pair of flyers rotating aboutacommonaxis that perpendicularly intersects the axis of the armaturecore, simultaneously lays two wires into two pairs of thecircumferentially spaced slots.

The orbit defined by each of the rotating flyers-defines a plane thatchordally intersects the laminated body or core at a distance from theaxis of the core determined by the design of the winding with which thearmature core is to be provided. Although the winding machine hasshrouds that embrace oppositesides of the core .and have smooth surfacedguide shoes to guide the wires into the slots in which they are wound,and hopefully keep the wires from snagging on the edges of the entrancesto the core slots, experience has demonstrated that this idealsituationis by no means an assured reality. Only too often the wire rubsacross one of the sharp edges defining the entrance to the wirereceiving slots as it enters the slot and, when that occurs, theinsulation on the wire is damaged and the wound armature becomes areject, or a potential failure in service.

The problem is especially serious when the design of the motor for whichthe armature is intended requires that the armature be wound with heavygage wire, and where the entrancesto the reentrant wire receiving slotsare narrow in order to minimize the interruptions in the cylindricalsurface of the armature core.

It was also discovered that the side thrust which the wire imposes onthe ends of the T-shaped teeth that separate the wire receiving slots asthe wire enters a slot, often deformed the teeth and actually caused theendmost laminations to turn on the shaft.

The present invention overcomes'all of these problems by the simpleexpedient of securing preformed plastic caps or shields to the oppositeends of the stack of laminations, which shields or capsare of the samesize and shape as'the laminationsandhave protective flanges projectingfrom the side thereof facing the laminations to embrace the ends of theteeth that separate the wire receiving slots and cover the edgesdefining the ends of the slots. Notonly do those shields or caps coverthe stems of the T-shaped teeth on several of the endmost laminations,but'also the heads thereof.

A significantly advantageous feature of the invention resides in thefact that thexplastic shields embrace the heads of the T-shaped teeth,without objectionably reducing the width ofthe slot entrances throughwhich the wire must pass as it is wound into the slots.

With these observations and'objectives in mind, the

manner in which the invention achieves its purpose will be appreciatedfrom thefollowing description andithe accompanying drawings, whichexemplify the, invention, it being understood that changesmay be madevin the precise'method of practicing the inventionand'in the specificproduct disclosed "herein without departing from the essentials of the.invention. setpforth in the .appended claims.

The accompanying drawings illustrate one. complete.

example of the embodiment of the invention con- I structed according tothe best mode so far devised for the practical application ofthe'principles thereof, and in which:

FIG. 1 is a side view of an armature core made. in accordance with thisinvention;

FIG. 2 is an exploded perspective view illustrating the procedure andtooling employed in assembling the stack of laminations and its plasticend shields or caps onto the shaft;

FIG. 3 is a detail view, at an enlarged scale, of the tops of twoadjacent T-shaped teeth which collectively form the peripheral portionof the laminated core body, and theportion of the plastic shield or capthat will embrace the adjacent ends of those teeth after the shield orcap is in position;

FIG. 4 is a view similar to FIG. 3 but showing how during application ofthe plastic shield or cap the heads of the T-shaped teeth are deformedand taperingly reduced in width towards the end of the stack, to

plane of the line 66, with a few coilsof wire in place.

for illustrative purposes.

Referring now particularly to the accompanying drawings, and especiallyto FIG. 1, the numeral 6designates the coil receiving body or core of anarmature core assembly made in accordance with this invention, and whichconsists of a stack of round laminations 7 punched from flat strip stockusually mild steel and press-fitted onto a shaft 8. A commutator 9 isalso mounted on the shaft.

The cylindrical periphery of the stack of laminations which comprise thecore is formed by the heads 10 of a circle of T-shaped teeth 11. Theteeth thus form between them a plurality of axially extendingcircumferentially spaced reentrant coil receiving slots 12, with narrowentrances 13 formed by the spacesbetween the heads of the T-shapedteeth. It should be noted that the width of these entrances is not manytimes greater than the diameter of the wire that is wound into thereentrant slots, a few coils of which are shown in FIG. 6, at 14.

Overlying each of the opposite ends of the laminated core of body 6 is apreformed plastic shield or cap 15. These shields or caps arepreferably'injection molded from Nylon, and hence. have great strength.They consist of'a flat disc 16 of the same size and shape as thelaminations 7, with a central hub 17 projecting from one side of thedisc. Since the disc 16 has the same shape as the laminations, itsperipheral portion consists of outwardly radiating circumferentiallyspaced T- shaped teeth or fingers l8. Along the edges of these teeth orfingers and uninterruptedly around the roots of the spaces between them,there are protective flanges 19 which project perpendicularly from theside of the disc 16 opposite that from which the hub 17 projects.

The protective flanges have portions 19a located at the undersides ofthe heads of the T-shaped teeth or fingers, and other portions 19b atthe opposite ends of the head of the T. Accordingly, when the shields orcaps are in place, they cover all of the edges at the ends of thelaminated body 6 with which the wire could conceivably come in contactduring the winding operation, and since the material of which theshields or caps are formed is smooth surfaced, all danger of having theinsulation onthe wire damaged in any way, is eliminated.

While the embracing relationship of the flanges 19 with the stems of theT-shaped teeth on several of the endmost laminations 7 inevitablyreduces the width of the wire-receiving slots at the opposite endsthereof, that reduction is inconsequential from the standpoint of spacefor the coils of wire that will be laid into those slots, and moreoverhas the beneficial effect of keeping the wire out of contact with thesides and bottom of the slots.

Another very important advantage that flows from having the flanges l9embrace the stems of the T- shaped teeth is the assurance that resultstherefrom that the endmost laminations will not be displacedrotationally about the shaft by the side thrust which the wire beinglaid into the slots imposes on the teeth. Because the flanges 19encompass all of the teeth on quite a number of the endmost laminations,the torque that results from the wire imposed side thrust issuccessfully resisted by even the slight keying action obtained fromhaving relatively slight longitudinally extending protrusions 20 on theshaft bite into the bore of the stack of laminations ash is pressed ontothe shaft.

Bearing in mind that the space between the heads of the T-shaped teeththat form the periphery of the laminated body or core 6 are quitenarrow, it is evident that unless space is made available for theportions 19b of the protective flanges that embrace the heads of the T-shaped teeth at the axially opposite ends of the stack of laminations,the presence of these flange portions would unduly restrict theentrances through which the wire initially enters the reentrant slots 12during the winding operation. That necessary space is made available bya novel deformation of the heads of the T- shaped teeth on a pluralityof the endmost laminations at both ends of the stack. This is done bycompressing or squeezing the heads of the teeth with a force that isprogressively less on the inwardly successive laminations. Thatsqueezing action taperingly enlarges the entrances to the wire receivingslots at both ends of the body or core 6, and thereby provides theneeded space for the protective flange portions 19b, as best seen inFIG. 4.

Also as best seen in FIG. 4, the circumferentional squeezing forceapplied to the heads of the T-shaped teeth on the laminations near theends of the stack, so deforms those heads that they assume a nestedwavelike shape that is more pronounced towards the ends of the stack.

While the compressive force that deforms the heads of the T-shaped teethat the opposite ends of the stack of laminations could be produced andapplied in different ways, in practice it is done by clamping the stackof laminations with the shields or caps 15 at the opposite ends thereofbetween a pair of shaping rings or tools 22 and 23 by means of asuitable press, not shown. Each of these shaping rings has a circle offingers 24 projecting from one side and, as shown in FIG. 2, they are soplaced in the press that the fingers of each ring point towards theother ring. The fingers are so located that they enter the spacesbetween the radiating teeth of the shields or caps 15 and project intothe slots in the laminated core or body as the shaping rings are forcedtowards each other by the press. On the radially outer faces of thefingers 24, there are wedges 25 that enter the spaces between the heads10 of the T-shaped teeth on the endmost groups of laminations. It is theentry of these wedges between the heads of the T-shaped teeth thatdeforms the heads and taperingly enlarges the entrances to the reentrantslots at the ends of the core to provide space for theprotective flangeportions 19b of the shields or caps 15.

Since the shields or caps are in place at the time the deformingoperation takes place, the compressive force is, of course, appliedthrough the flange portions 19b.

As a result, the radially outermost portions of the shields or capstightly hug the heads of the T-shaped teeth of the armature core andcover the same for an appreciable distance inwardly of the ends of thecore, without objectionably restricting the entrances of the wirereceiving slots of the core.

While for the reasons just stated it is preferable to apply the shapingforce to the heads of the T-shaped teeth of the armature core with theplastic shields or caps in place, it could be done before the shields orcaps are applied to the ends of the core, but obviously this wouldentail another operation.

In practice, is has been found desirable to first press fit thecommutator onto the shaft, then slide the plastic shield or cap which isto cover the adjacent end of the laminated core onto the shaft, with itshub facing the commutator. The stack of laminations and the other shieldor cap are then placed in the press with the shield bottommost andsetting on the bottom shaping ring 23. The shaft, with the commutatorand shield in place thereon, is then inserted into the bore of the stackof laminations with the commutator end of the shaft uppermost; The pressis now activated and, in one operation, the shaft is driven into andthrough the stack of laminations and the heads of the T-shaped teeth atthe opposite ends of the stack are subjected to the circumferentialsqueezing force that gives them the desired tapered shape.

As the stack of laminations is forced onto the shaft by the closingaction of the press, the key forming ridges 20 on the shaft bite intothe laminations to secure the same against rotation relative to theshaft, and as the press opens a conventional spring loaded ejector liftsthe assembly off the lower shaping ring 23. Upon removal of the assemblyfrom the press, a C-washer 30 is applied to the shaft to provide athrust bearing surface at the end of the hub of the shield that isremote from the commutator.

While the plastic shields or caps greatly improve the armature core bycovering all edges on the ends of the core that could damage theinsulation of the wire as it is wound onto the core, the deformation ofthe heads of the T-shaped teeth at the axially opposite ends of the corein the manner described even without the protection afforded by theshields or caps, results in a significantly improved armature core. Thisfollows from the fact that the deformation bends the ends of the headsof the T-shaped teeth axially inward and thus converts an otherwisesharp edge or comer into a smooth surface across which the wire canslide without damage to its insulation.

Those skilled in the art will appreciate that the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

The invention is defined by the following claims:

1. The method of making an electric motor armature, wherein a stack ofpunched laminations, each of which has a circular row of substantiallyT-shaped teeth defining its circumference said teeth having headsdefined by the cross member of the T, is assembled in alignedrelationship on a shaft to form a cylindrical core havingcircumferentially spaced reentrant winding receiving slots opening toits periphery through narrow axially extending slots formed by thespaces between the heads of the circumferentially adjacent teeth of thelaminations, said method being characterized by:

deforming the heads of the T-shaped teeth on a plurality of the endmostlaminations at both ends of the stack by bending the extremities of theheads inwardly with a progressively lesser curvature on the inwardlysuccessive laminations, to thereby taperingly enlarge the entrances tothe winding receiving slots at both ends of the core and provide smoothsurfaces for said entrances.

2. The method of claim 1, wherein said deformation of the heads of theT-shaped teeth is done by inserting a wedge between adjacent teeth.

3. The method of making an electric motor armature, wherein a stack ofpunched laminations, each of which has a circular row of substantiallyT-shaped teeth defining its circumference said teeth having headsdefined by the cross member of the T, is assembled in alignedrelationship on a shaft to form a cylindrical core havingcircumferentially spaced reentrant winding receiving slots opening toits periphery through narrow axially extending slots formed by thespaces between the heads of the circumferentially adjacent teeth of thelaminations, said method being characterized by:

circumferentially squeezing the heads of the T- shap'ed teeth on aplurality of the endmost laminations at both ends of the stack with aforce that is progressively less on the inwardly successive laminationsto thereby deform the heads of the T- shaped teeth on said inwardlysucessive laminations to a progressively less degree and taperinglyenlarge the entrances to the winding receiving slots at both ends of thecore.

4. The method of claim 3, further characterized in that said deformationof the heads of the T-shaped teeth is performed with a tool that haswedge-shaped lugs positioned to enter the spaces between the heads ofthe T-shaped teeth as said tool is forced axially towards the stack.

5. The method of claim 4, further characterized by covering the ends ofthe stack of laminations with preformed plastic shields of a size andshape substantially corresponding to that of the endmost laminations.

6. The method of claim 5, wherein the ends of the heads of those of theT-shaped teeth that are deformed are covered by portions of the plasticshields, and the presence of said portions of the shields isaccommodated by said deformation of the heads of the T-shaped teeth.

7. The method of claim 6, further characterized in that said portions ofthe shields are interposed between opposite ends of the heads of theteeth and the wedge-shaped lugs of said tool as the latter is forcedaxially towards the stack, so that the tooth-head deforming force isapplied through said portions of the plastic shields and said portionsof the plastic shields are driven tightly against the ends of the headsof the T- shaped teeth. v

8. The method of makingan electric motor armature, wherein a stack ofpunched laminations, each of which has a circular row of substantiallyT-shaped teeth defining its circumference said teeth having headsdefined by the cross member of the T, is assembled in alignedrelationship on a shaft to form a cylindrical core havingcircumferentially spaced reentrant winding receiving slots opening toits periphery through narrow axially extending slots formed by thespaces between the heads of the circumferentially adjacent teeth of thelaminations, said method being characterized by:

A. providing preformed plastic shields for the ends of the stack oflaminations of a size and shape substantially corresponding to the sizeand shape of the laminations, but with protective flanges projectingfrom one face thereof to embrace the T- shaped teeth on the endmostlaminations of the stack;

B. with one of said shields overlying an end of the stack of laminationswith the protective flanges of the shield facing said end of the stack,forcing said shield against the adjacent end of the stack with theprotective flanges on the shield covering the edges of the teeth on theendmost laminations; and

C. deforming the heads of the T-shaped teeth on a plurality of theendmost laminations of the stack with a circumferentially actingcompression force applied through the contiguous protective flangeportions and that has progressively less effect on the inwardlysuccessive laminations to thereby axially outwardly taperingly reducethe width of the heads of the teeth and make room for the contiguousprotective flanges on the shield, whereby the presence of saidprotective flanges does not objectively diminish the width of theadjacent entrances to the winding receiving slots.

9. The method of claim 8 wherein the shield is forced against theadjacent end of the stack of laminations and the heads of the T-shapedteeth are deformed at the same time by forcing a tool that haswedge-shaped lugs positioned to enter the spaces between the heads ofthe T-shaped teeth, axially towards the stack.

10. The method of claim 9, further characterized in that one of saidshields is forced against each of the opposi'te ends of the stack oflaminations and said toothhead deforming operation takes place at eachend of the stack, and wherein said operations are performed by axiallyclamping the stack and the shields at the ends thereof between a pair ofsaid tools.

1. The method of making an electric motor armature, wherein a stack ofpunched laminations, each of which has a circular row of substantiallyT-shaped teeth defining its circumference said teeth having headsdefined by the cross member of the T, is assembled in alignedrelationship on a shaft to form a cylindrical core havingcircumferentially spaced reentrant winding receiving slots opening toits periphery through narrow axially extending slots formed by thespaces between the heads of the circumferentially adjacent Teeth of thelaminations, said method being characterized by: deforming the heads ofthe T-shaped teeth on a plurality of the endmost laminations at bothends of the stack by bending the extremities of the heads inwardly witha progressively lesser curvature on the inwardly successive laminations,to thereby taperingly enlarge the entrances to the winding receivingslots at both ends of the core and provide smooth surfaces for saidentrances.
 2. The method of claim 1, wherein said deformation of theheads of the T-shaped teeth is done by inserting a wedge betweenadjacent teeth.
 3. The method of making an electric motor armature,wherein a stack of punched laminations, each of which has a circular rowof substantially T-shaped teeth defining its circumference said teethhaving heads defined by the cross member of the T, is assembled inaligned relationship on a shaft to form a cylindrical core havingcircumferentially spaced reentrant winding receiving slots opening toits periphery through narrow axially extending slots formed by thespaces between the heads of the circumferentially adjacent teeth of thelaminations, said method being characterized by: circumferentiallysqueezing the heads of the T-shaped teeth on a plurality of the endmostlaminations at both ends of the stack with a force that is progressivelyless on the inwardly successive laminations to thereby deform the headsof the T-shaped teeth on said inwardly sucessive laminations to aprogressively less degree and taperingly enlarge the entrances to thewinding receiving slots at both ends of the core.
 4. The method of claim3, further characterized in that said deformation of the heads of theT-shaped teeth is performed with a tool that has wedge-shaped lugspositioned to enter the spaces between the heads of the T-shaped teethas said tool is forced axially towards the stack.
 5. The method of claim4, further characterized by covering the ends of the stack oflaminations with preformed plastic shields of a size and shapesubstantially corresponding to that of the endmost laminations.
 6. Themethod of claim 5, wherein the ends of the heads of those of theT-shaped teeth that are deformed are covered by portions of the plasticshields, and the presence of said portions of the shields isaccommodated by said deformation of the heads of the T-shaped teeth. 7.The method of claim 6, further characterized in that said portions ofthe shields are interposed between opposite ends of the heads of theteeth and the wedge-shaped lugs of said tool as the latter is forcedaxially towards the stack, so that the tooth-head deforming force isapplied through said portions of the plastic shields and said portionsof the plastic shields are driven tightly against the ends of the headsof the T-shaped teeth.
 8. The method of making an electric motorarmature, wherein a stack of punched laminations, each of which has acircular row of substantially T-shaped teeth defining its circumferencesaid teeth having heads defined by the cross member of the T, isassembled in aligned relationship on a shaft to form a cylindrical corehaving circumferentially spaced reentrant winding receiving slotsopening to its periphery through narrow axially extending slots formedby the spaces between the heads of the circumferentially adjacent teethof the laminations, said method being characterized by: A. providingpreformed plastic shields for the ends of the stack of laminations of asize and shape substantially corresponding to the size and shape of thelaminations, but with protective flanges projecting from one facethereof to embrace the T-shaped teeth on the endmost laminations of thestack; B. with one of said shields overlying an end of the stack oflaminations with the protective flanges of the shield facing said end ofthe stack, forcing said shield against the adjacent end of the stackwith the protective flanges on the shield covering the edges of Theteeth on the endmost laminations; and C. deforming the heads of theT-shaped teeth on a plurality of the endmost laminations of the stackwith a circumferentially acting compression force applied through thecontiguous protective flange portions and that has progressively lesseffect on the inwardly successive laminations to thereby axiallyoutwardly taperingly reduce the width of the heads of the teeth and makeroom for the contiguous protective flanges on the shield, whereby thepresence of said protective flanges does not objectively diminish thewidth of the adjacent entrances to the winding receiving slots.
 9. Themethod of claim 8 wherein the shield is forced against the adjacent endof the stack of laminations and the heads of the T-shaped teeth aredeformed at the same time by forcing a tool that has wedge-shaped lugspositioned to enter the spaces between the heads of the T-shaped teeth,axially towards the stack.
 10. The method of claim 9, furthercharacterized in that one of said shields is forced against each of theopposite ends of the stack of laminations and said tooth-head deformingoperation takes place at each end of the stack, and wherein saidoperations are performed by axially clamping the stack and the shieldsat the ends thereof between a pair of said tools.